ARM: dts: Add SPI nodes to the exynos5420 device tree file

Add SPI device tree nodes to Exynos5420 SoC

Signed-off-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Leela Krishna Amudala <l.krishna@samsung.com>
Reviewed-by: Andrew Bresticker <abrestic@chromium.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>